Defense Secretary Ashton B. Carter told reporters Thursday that the camps contained militants “actively plotting” attacks in Europe and that the strikes were “critically important.”
“As always, external operations are a very important part of the reason to destroy ISIL, as well as to wipe them out of Libya itself,” Carter said, using an acronym for the Islamic State.
MQ-9 armed drones also participated in the strikes, using Hellfire missiles to hit targets that remained after the initial bombardment, Col. Patrick Ryder, an Air Force spokesman, told reporters. The operation took 34 hours, and the two B-2s, named the Spirit of Pennsylvania and the Spirit of Georgia, flew from Whiteman Air Force Base in Missouri to carry out the strikes, Ryder said. The camps were in remote desert locations, and no civilians were believed to have been hit in the bombardment, officials said.
The militants declared Sirte the capital of their Libyan caliphate less than a year ago. U.S. aircraft began pounding the city with airstrikes in August in an effort to support Libyan government ground forces. Western Special Operations troops, including a small contingent of Americans, also helped in the offensive.
In total, the United States launched more than 500 airstrikes in the air campaign, called Operation Odyssey Lightning. Toward the end of the mission, a small pocket of Islamic State fighters in downtown Sirte proved especially resilient, forcing a weeks-long effort of concerted strikes and heavy ground fighting before the roughly dozen or so fighters were killed or surrendered.
The U.S. military has other aircraft based much closer to Libya than Missouri, but the Pentagon chose the B-2s for their ability to drop many bombs in a short time span and loiter overhead for a long time, Ryder said. Each plane can carry 40,000 pounds, and up to 80 500-pound bombs known as Joint Direct Attack Munitions (JDAMs). The B-2 has not been used in combat since 2011, when they they were part of Operation Odyssey Dawn.
The Washington Post reported in November that the Pentagon had been quietly preparing for follow-on strikes once Sirte was liberated, focusing intelligence-gathering assets and surveillance aircraft on the fighters who fled the city as their defenses crumbled.
This story was originally published at 9:06 a.m. and updated with additional information.